Families may hold the key to living to 100 years and beyond, scientists believe.

Research carried out in the US suggests that some families are predisposed to long and healthy lives.

It found that people are much more likely to celebrate their 100th birthday if their brother or sister has hit the milestone.

This survival advantage is likely due to genetics and environmental factors

Dr Evan Hadley, US National Institute for Aging

The scientists believe that genes combined with environmental factors may explain the pattern.

Dr Thomas Perls, director of the New England Centenarian Study in Boston and Dr John Wilmoth of the University of California, based their theory on a study of 444 American families.

Long lives

Each of the families had at least one member who lived to 100 years of age or longer.

They found that brothers of centenarians were 17 times more likely to reach 100 compared to the general population.

Similarly, sisters of centenarians were eight times more likely to celebrate their 100th birthday compared to other people.

The study also showed that the siblings of centenarians were generally healthier than the population as a whole.

Sisters of centenarians were about 50% less likely to die prematurely compared with other people.

Brothers of centenarians had similarly low death rates.

The findings, published in the latest issue of the journal Proceedings of the National Academy of Sciences, back up previous studies which have suggested a link between long lives and families.

Previous research by Dr Perl found that siblings of centenarians were four times more likely to live into their early nineties than the general population.

University of Utah researchers found brothers, sisters and other first-degree relatives of the long-lived tend to live longer than cousins and other more distant relatives.

Gene key

This led scientists to suggest that a small number of genes might influence exceptional longevity.

Last year, Dr Perl and colleagues found a region on chromosome 4 that is "highly suggestive" of genetic predisposition to long life.

Dr Evan Hadley, associate director for geriatrics and clinical gerontology at the US National Institute for Aging, said the role played by genes in determining long life was still unclear.

He said: "This striking finding provides further evidence that centenarians and their relatives are a special group in that they appear to be more resistant to disease or they survive disease better throughout the lifespan.

"This survival advantage is likely due to genetics and environmental factors, but the roles of each of these factors are still unclear.

"Studying these individuals could help us understand the factors that contribute to long, healthy lives."